Rare earth magnet question

janitorjerm · Jul 17, 2012

Are these a good size and strength for my stir plate or are they too much or too little? I did a search on the magnet but didn't find anything. All help appreciated.

http://www.magnet4less.com/product_info.php?cPath=11&products_id=1114

beau_cephus · Jul 17, 2012

I picked up 10 5mm Dia x 3mm thick Rare Earth magnets from these guys http://stores.ebay.com/bluestone002 on ebay.

I just installed them on my DIY stirplate and they worked well with my 1" stir bar when placed directly on top of the stir plate. I dont have a flat bottom glass container to test it out with.

I probably have 1/8" (3mm) gap between my magnets and bottom side of my cigar box. The cigar box top is probably 1/8"

janitorjerm · Jul 17, 2012

Is a 1" stir bar the "norm"?

rekoob · Jul 17, 2012

I used a hard drive magnet, I think if your using two of them you should be okay. I also use a 1" stir bar and a few of the containers i use don't have flat bottomes but the stir bar stays in place. I even used a 1 gal jug a couple times and the 1" stir bar worked fine.

janitorjerm · Jul 17, 2012

If I could find a hard drive that would have been first choice but it seems like when you need something you can't remember where you put it. I was going to use two or three of these magnets instead.

rekoob · Jul 17, 2012

a few others have said they doubled up on the magnets and it worked great so you shouldn't have any issues.

janitorjerm · Jul 17, 2012

So should I get them thicker or stack them

DSmith · Jul 17, 2012

The ones in the link should work well in a flat bottomed flask.

I put a pair of these on a fan and the magnetic field is crazy, 1-5/8" stirbar always self-centers in a with a curved bottom gallon jug.

http://www.grainger.com/Grainger/Disc-Magnet-2VAF2?Pid=search

janitorjerm · Jul 17, 2012

I just ordered similar ones in 7/16 from a different site. They may be magnets4less but they are shipping for more. They tacked five bucks on my order for being less than five dollars and the minimum shipping they offered was ten dollars. Seems a bit steep to me .

janitorjerm · Jul 17, 2012

Here is what I went with.

https://www.kjmagnetics.com/proddetail.asp?prod=D72-N52

Frodnetso · Jul 17, 2012

These are the ones I used. I stacked up two high, two stack with opposite poles up. Next time I would try a bar magnet.

https://www.kjmagnetics.com/proddetail.asp?prod=D64%2DN52

janitorjerm · Jul 17, 2012

So they didn't work very well?

DSmith · Jul 17, 2012

Hardware store velcro with a sticky-back works great for trying magnets. You can cover the top circle of the fan with the fuzzy part and the plastic part hook part trimmed to the magnet. It's strong enough of a bond to leave in your final configuration, never need glue.

janitorjerm · Jul 17, 2012

Hopefully the magnets I purchased will be sufficient. Now I just need to find a stir bar and flask.

TheZer · Jul 18, 2012

Cheap, also stackable for easy height adjustment.
HarborFreight

william_shakes_beer · Jul 18, 2012

I used 2 hard drive magnets. If you're glueing them to a computer fan, you need to install a non metallic spacer of about 1/2" thick so the magnets won't interfere with the magnets in the motor.

beau_cephus · Jul 21, 2012

I was able to get my stirplate working last night. Picked up these from local harbor freight and stacked them 4 high. Had issues with it throwing the stir bar so i replaced my 12V power supply with a 5V supply. Tried a 9V and still had issues with the stir bar.

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